I only own one lever action, a Winchester 1892 clone in .44mag/.44 spl. I don't know if this is common to other lever action models, but loading is somewhat awkward in that either the gate catches your thumbnail, or you have to be careful to push the round in far enough that the gate holds it by friction, allowing you to push it the rest of the way in with the next round. But, don't load it far enough and the gate won't hold it, allowing it to slip back out.
The Marlin design and later Winchester 94 rifles manage this a bit better than the 92 action. You can still pinch your thumb if you aren’t careful but like “Garand Thumb” you pretty quickly learn the drill.
Wild West Guns makes a light mount that clamps to the magazine tube, that would look / work a bit better than that offset mount.